What is a «feature»?

The performance of these simple machine learning algorithms depends heavily on the representation of the data they are given.
For example, when logistic regression is used to recommend cesarean delivery, the AI system does not examine the patient directly.
Instead, the doctor tells the system several pieces of relevant information, such as the presence or absence of a uterine scar.
Each piece of information included in the representation of the patient is known as a feature.

Goodfellow, Bengio, Courville - «Deep Learning» (2016)